Self-retaining roof bolt

Abstract

A self-retaining roof bolt comprising an elongated U-shaped member having a pair of spaced legs which support a flat plate fitted over the U-shaped member and are held under transverse tension at ambient temperature by a grouting which becomes malleable at elevated temperatures. The roof bolt is installed in a roof hole by momentarily heating the leg sections, which causes the grouting to soften, releasing the tension on the legs and allowing them to separate and wedge against the roof hole walls. Thus, the bolt retains itself in the roof hole while the grouting cools. Upon cooling, the grouting re-solidifies, firmly securing the bolt.

What is claimed is: 
     
       1. A self-retaining roof bolt comprising: a. an elongated U-shaped member having a pair of spaced leg sections depending from the connection portion of said U-shaped member, said leg sections being formed to support a flat plate fitted over said U-shaped member;   b. a grouting coated on said U-shaped member to maintain said leg sections under transverse tension at ambient temperature, said grouting being malleable at elevated temperatures;   c. a flat plate having an opening therein positioned over said U-shaped member and supported by said leg sections, said opening being large enough to permit said leg sections to move transversely on release of said transverse tension a sufficient amount to maintain said U-shaped member in place in a roof hole; and   d. a gasket abutting said flat plate member and in sealing engagement with the lower portion of said U-shaped member to prevent flow of said coating below said plate at elevated temperature.   
     
     
       2. A roof bolt in accordance with claim 1 wherein the free ends of the leg sections are formed in opposing directions at an angle of approximately 90° to the longitudinal centerline of the U-shaped member. 
     
     
       3. A roof bolt in accordance with claim 2 wherein the coating is a sulfur-based compositon. 
     
     
       4. A roof bolt in accordance with claim 2 wherein the closed end of the leg sections is formed as a continuous bend. 
     
     
       5. A roof bolt in accordance with claim 4 wherein the U-shaped member is steel. 
     
     
       6. A roof bolt in accordance with claim 1 wherein the bolt is 4 to 6 feet in length and about 1 inch in diameter. 
     
     
       7. A roof bolt in accordance with claim 1 wherein the flat plate is steel. 
     
     
       8. A method of installing the roof bolt defined in claim 1 which comprises heating the free ends of the leg sections of the U-shaped member of the bolt until the grouting becomes malleable releasing the tension on the leg sections of the U-shaped member causing the leg sections to wedge against the roof hole and flowing to substantially fill the voids between the hole walls and the bolt. 
     
     
       9. A method according to claim 8 wherein heating is accomplished by passing an electrical current through the U-shaped member.